An apparatus includes a photosensor for detecting change of the state of the apparatus such as a photosensor detecting that a document is started to be transferred. In such an apparatus, an operation mode is switched between a normal mode and a sleep mode based on a detection result made by the photosensor. A driving section is activated in the normal mode, and power of the driving section is turned off in the sleep mode. Accordingly, consumption power can be reduced in the apparatus. It is known that the photosensor emits light to be lit on continuously in the normal mode and emits light to be lit on intermittently in the sleep mode. This shortens a light emission period of the photosensor in the sleep mode and consumption power can be further reduced.